This invention relates to circuit breaker actuaing devices, and more particularly it is concerned with a circuit breaker actuating device comprising valve means constructed to permit an operation fluid to pass therethrough in a large quantity in a short time interval upon receipt of an actuation signal, no matter how small in size it may be.
In recent years, there has been an increasing demand for electric power, and power systems have accordingly been increased in capacity. If a short circuit occurs in such power system of high capacity, the accident will spread to associated parts and operations of the system as a whole will have to be suspended, unless the part damaged by the accident is immediately cut off from the system. As the result of such accident, failure of power supply may occur over a wide area for a prolonged period. In order to avoid such accident, circuit breakers employed as means for protecting power systems by interrupting a current should be capable of interrupting a current at high speed. This requirement must be met especially in cases where circuit breakers are of the type which is capable of interrupting a current of super-high voltage and value. Circuit breakers of this type should be capable of effecting two-cycle interruption.
An increase in the capacity of an electric power system makes it necessary to use circuit breakers of a higher interrupting capacity. This entails the need to use a very high force to actuate the interrupting part of such circuit breaker, and consequently an actuating device adapted to actuate the circuit breaker involved should be able to produce a high operation force and act at high speed.
In one type of circuit breaker actuating devices known in the art adapted to produce a high operation force, compressed air or other operation fluid is caused to act on a piston to produce a high operation force. Means for feeding an operation fluid to the piston and causing the fluid to act on the latter should be constructed such that the operation fluid can flow therethrough in a large quantity in a short time interval in order to actuate the piston at high speed. However, it is not possible to produce an operation signal of a large size to render the circuit breaker actuating device operative in view of the capacity of the power source and other factors. Difficulty is thus experienced in directly actuating the value means by the operation signal, so that it becomes necessary to amplify the operation signal to actuate the valve means.
To amplify the operation signal requires the provision of a number of amplifier valves. However, the provision of a number of amplifier valves defeats the object of actuating the circuit breaker actuating device at high speed, because the time required for actuating the amplifier valves is a dead time which has nothing to do with rendering the actuating device operative.
Proposals have been made to obviate this disadvantage by reducing the number of amplifier valves while increasing the capacity of each valve to amplify an operation signal. Such proposals have been unsuccessful in obviating the problem because an increase in the amplification rate of each amplifier valve results in an increase in the operation time of the valve. Thus, the reduction in the number of amplifier valves used does not necessarily lead to an increase in the speed at which the circuit breaker actuative device is rendered operative.